1. Field of the Invention
The present invention relates to a mobile body surrounding surveillance apparatus for surveillance of safety during movement of a manned or unmanned mobile body, such as a ship or a car (a vehicle, such as a two-wheeled vehicle (e.g., a motorcycle or a bicycle), a four-wheeled vehicle (e.g., an automobile), a train, etc.), a human or the like. For example, when a mobile body (own mobile body) moves laterally and there is a risk such that the mobile body contacts or collides with another mobile body (other mobile body) existing therearound, the mobile body surrounding surveillance apparatus is used to assist confirming the safety by warning a human involved with the mobile body by informing the danger caused by the approach of the other mobile body. The present invention also relates to a mobile body surrounding surveillance method using the mobile body surrounding surveillance apparatus, a control program for causing a computer to execute the mobile body surrounding surveillance method, and a computer-readable recording medium recording the control program.
2. Description of the Related Art
A recent increase in accidents of mobile bodies, such as traffic accidents (e.g., collision of automobiles, etc.) raises a significant public concern. Particularly, when moving an automobile to the left or right to make a lane change or turning right or left, a collision or crash frequently occurs in spite of the automobile driver's caution. The reason for such collision or crash is considered as follows: the automobile driver does not sufficiently confirm a rear and side direction with respect to the moving direction of his/her driving car (own mobile body) using a rearview mirror or the like; or there is another car (another mobile body) which is not covered by a rearview mirror or the like, i.e., a so-called blind spot.
To prevent such a traffic accident, for example, Japanese Laid-Open Publication No. 2000-285245 discloses a mobile body crash prevention apparatus which takes an image of a rear view using a camera mounted on a car, detects the presence of another car from the captured image, and employs an informing section to inform the driver of the car of the approach of another car by giving a warning, if there is a risk of collision or crash of another car coming in a rear and side direction when moving to the left or right (e.g., making a lane change, etc.) or turning left or right.
With the mobile body crash prevention apparatus, line edges which constitute a white line on a road or a ridge line of the road, and a vanishing point (point at infinity) which is an intersection of the line edges, are detected in each image of a plurality of frames captured in time series by the capturing section. Based on the white line and the ridge line and the positional information of the vanishing point, a detection region is narrowed. The detection region is divided into small regions (blocks). Movement amounts of the small regions between each frame are calculated by a technique called optical flow. In this case, the detection region is a region E which is about a half of a screen indicated by slanted dashed lines in FIG. 10. The movement amount information thus calculated is used to detect, for example, a passing car rapidly approaching from a rear and side direction.
However, the conventional mobile body crash prevention apparatus of Japanese Laid-Open Publication No. 2000-285245 has the following problem.
When driving, a white line is detected to confirm a lane, a vanishing point is calculated to obtain the moving direction of another car, and optical flow is used to determine how each block obtained by dividing the detection region is moved. Thus, advanced computation is required. In addition to the computation quality, the computation amount is huge, because the large image region E which is about a half of a screen indicated by slanted dashed lines in FIG. 10 is required as a detection region.
Thus, real-time processing cannot be performed due to the huge computation amount. To reduce the computation amount, a method of predicting a movement amount associated with the passage of time is used, for example. Therefore, the movement direction of another oar cannot be correctly detected, likely leading to occurrence of error. Further, some roads may have no white lines, so that the movement amount of the mobile body cannot be calculated. Thus, the apparatus is not practical.